Protection of electronic devices used with perforating guns

ABSTRACT

A sensing subassembly for use with a downhole tool comprises a housing, a cavity disposed within the housing, at least one electronic component disposed within the cavity, and at least one isolating member disposed within the cavity. The at least one isolating member is configured to attenuate at least a portion of frequency components of a mechanical wave above a threshold and transmit at least a portion of frequency components below the threshold to the at least one electronic device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage of and claims priority under 35U.S.C. §371 to International Patent Application Serial No.PCT/US12/70740, filed on Dec. 19, 2012, entitled “Protection ofElectronics Used with Perforating Guns,” by Patrick L. Walter, et al.,which claims the benefit of and priority under 35 U.S.C. §119 to U.S.Provisional Patent Application Ser. No. 61/732,322, filed on Dec. 1,2012, entitled “Protection of Electronics used with Perforating Guns,”by John P. Rodgers, et al., both of which are incorporated herein byreference in their entirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Hydrocarbons may be produced from wellbores drilled from the surfacethrough a variety of producing and non-producing formations. Forexample, a casing string may be set and cemented in the wellbore, and/ora liner may be hung in the casing string. The casing string and cementgenerally form an impervious barrier between the wellbore interior andthe surrounding subterranean formation. In order to provide fluidcommunication through the casing and cement, the casing string may beperforated by firing a perforation gun or perforation tool. Perforationguns generally include an explosive charge such as a shaped explosivecharge that detonates to form a jet, which may penetrate the tool, thecasing, any cement, and form a perforation tunnel in the subterraneanformation. In general multiple perforating charges are used per intervalto create a plurality of opening for fluid to pass from the subterraneanformation into the wellbore (e.g., production fluids such as oil, water,and/or gas) and/or for fluids to pass from the wellbore to thesubterranean formation (e.g., treatment fluids, injection fluids, etc.).

In general, the resulting detonation of the perforating charge(s) maycreate a high intensity shock wave impacting the perforating tools, andeventually propagating as pressure disturbance through the wellbore. Theimmediate shock wave and resulting pressure disturbance may result invarious forces being applied to the components disposed within thewellbore, which in some cases may result in damage and/or failure of thecomponents.

SUMMARY

In an embodiment, a sensing subassembly for use with a downhole toolcomprises a housing, a cavity disposed within the housing, at least oneelectronic component disposed within the cavity, and at least oneisolating member disposed within the cavity. The at least one isolatingmember is configured to attenuate at least a portion of frequencycomponents of a mechanical wave above a threshold and transmit at leasta portion of frequency components below the threshold to the at leastone electronic device.

In an embodiment, a method of measuring a shock event in a wellborecomprises receiving, by a sensing subassembly, at least one mechanicalwave within a wellbore, where the sensing subassembly comprises: acavity disposed within a housing, at least electronic component disposedwithin the cavity, and at least one isolating member disposed with theat least one electronic device within the cavity. The method alsocomprises attenuating at least a portion of frequency components of theat least one mechanical wave above a threshold frequency, transmittingat least a portion of the frequency components of the at least onemechanical wave below the threshold to the electronic device, sensing atleast one parameter associated with the at least one mechanical wave,generating, by the electronic component, at least one signal in responseto the sensing, and storing the at least one signal in a non-transitorycomputer readable media.

In an embodiment, a method of absorbing a mechanical wave using a shockprotection apparatus comprises receiving a mechanical wave at a housing.The housing is disposed in a wellbore, and the housing contains at leastone cavity with at least one sensor disposed within the at least onecavity. The at least one sensor is coupled to the housing by anisolation member. The method also comprises attenuating at least aportion of the mechanical wave using the isolation member, transmittingat least a portion of the mechanical wave to the at least one sensorusing the isolation member, and sensing at least one parameter of themechanical wave transmitted to the at least one sensor.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and theadvantages thereof, reference is now made to the following briefdescription, taken in connection with the accompanying drawings anddetailed description:

FIG. 1 is a schematic partial cross-sectional view of an embodiment of awell system and associated method which can embody principles of thepresent disclosure.

FIGS. 2-5 are schematic views of an embodiment of a sensor which may beused in the system and method of FIG. 1.

FIG. 6 is a schematic view of an embodiment of sensor configurations.

FIGS. 7A-7B are schematic views of embodiments of sensor configurations.

FIG. 8 is still another schematic view of an embodiment of sensorconfigurations.

FIG. 9A is yet another schematic view of an embodiment of sensorconfigurations.

FIG. 9B is another schematic view of an embodiment of sensorconfigurations.

FIG. 9C is still another schematic view of an embodiment of sensorconfigurations.

FIG. 10 is yet another schematic view of an embodiment of sensorconfigurations.

FIG. 11 is another schematic view of an embodiment of sensorconfigurations.

FIG. 12 is still another schematic view of an embodiment of sensorconfigurations.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the drawings and description that follow, like parts are typicallymarked throughout the specification and drawings with the same referencenumerals, respectively. The drawing figures are not necessarily toscale. Certain features of the invention may be shown exaggerated inscale or in somewhat schematic form and some details of conventionalelements may not be shown in the interest of clarity and conciseness.Specific embodiments are described in detail and are shown in thedrawings, with the understanding that the present disclosure is to beconsidered an exemplification of the principles of the invention, and isnot intended to limit the invention to that illustrated and describedherein. It is to be fully recognized that the different teachings of theembodiments discussed infra may be employed separately or in anysuitable combination to produce desired results.

Unless otherwise specified, any use of any form of the terms “connect,”“engage,” “couple,” “attach,” or any other term describing aninteraction between elements is not meant to limit the interaction todirect interaction between the elements and may also include indirectinteraction between the elements described. In the following discussionand in the claims, the terms “including” and “comprising” are used in anopen-ended fashion, and thus should be interpreted to mean “including,but not limited to . . . ”. Reference to up or down will be made forpurposes of description with “up,” “upper,” or “upward” meaning towardthe surface of the wellbore and with “down,” “lower,” or “downward”meaning toward the terminal end of the well, regardless of the wellboreorientation. Reference to in or out will be made for purposes ofdescription with “in,” “inner,” or “inward” meaning toward the center orcentral axis of the wellbore, and with “out,” “outer,” or “outward”meaning toward the wellbore tubular and/or wall of the wellbore.Reference to “longitudinal,” “longitudinally,” or “axially” means adirection substantially aligned with the main axis of the wellboreand/or wellbore tubular. Reference to “radial” or “radially” means adirection substantially aligned with a line between the main axis of thewellbore and/or wellbore tubular and the wellbore wall that issubstantially normal to the main axis of the wellbore and/or wellboretubular, though the radial direction does not have to pass through thecentral axis of the wellbore and/or wellbore tubular. The variouscharacteristics mentioned above, as well as other features andcharacteristics described in more detail below, will be readily apparentto those skilled in the art with the aid of this disclosure upon readingthe following detailed description of the embodiments, and by referringto the accompanying drawings.

The use of a perforating tool or other detonation device within awellbore may result in a mechanical shock disturbance due to adetonation and/or perforating event. For clarity, a mechanical shockdisturbance, a shock wave, and/or a pressure disturbance in the wellboreare collectively referred to as “mechanical waves” herein, wherein“mechanical waves” refer to any wave needing a medium in order topropagate (as opposed to an electromagnetic wave that can propagate in avacuum). Mechanical waves may propagate as pressure waves in the fluidwithin a wellbore, and/or as transverse, longitudinal, and/or surfacewaves in the fluid or components of the wellbore (e.g., the wellboretubular, the casing, the sensing subassembly housing, etc.). The impacton the perforating tool, the wellbore tubular string coupled to theperforating tool, and various other components within the wellbore(e.g., packers, plugs, etc.) may result in damage to the variouscomponents. Models may be used to simulate the results of a perforatingevent to allow tool strings to be designed that are capable ofwithstanding the perforating event. In order to calibrate the models,actual perforating event data can be used, which may be collected usingsensors at or near the perforating location. For example, pressuresensors, accelerometers, temperature sensors, and the like may be placedwithin the perforated zone to collect data before, during, and after thedetonation of one or more explosive devices. The resulting data may thenbe used in the development of a model or simulating tool for the designof the perforating tool, wellbore tubular string, and/or other variouscomponents impacted by the perforating event.

The sensors used to collect the perforating event data may themselves besubjected to the forces created by the perforating event. It will beappreciated that the sensors should be subjected to some portion of theresulting forces in order to obtain suitable measurements, however,excess exposure to the resulting forces may damage or destroy thesensors and the associated processing and storage equipment. In order tolimit or prevent damage to the sensors themselves, a shock protectionapparatus may be used to limit or control the impact of the forcesresulting from the mechanical waves.

As disclosed herein, the configuration of the shock protection apparatusmay vary depending on the type of sensor or other electronic componentbeing protected. Mechanical waves generated by detonation may travelfrom the guns and a detonating cord housing through the tools. Themechanical waves may reflect off of boundaries resulting in many wavesbeing imparted on sensitive components, with the possibility ofconstructive interference. Mechanical waves reaching sensitivecomponents may result in acceleration above a threshold levelexperienced by the components. This acceleration can result in localizedstress and deformation in the components that can lead to damage and/orfailure. Isolation mounts may serve to filter out frequencies above athreshold from mechanical waves, resulting in accelerations below athreshold on the sensitive components. Stiffeners such as metal stripsand/or tubes may engage electronic boards to reduce and/or limit themaximum flexing and/or deformation of the components therein. Forexample, a metal strip stiffener may engage an electronic board toreduce the flexing of the electronic board. The metal strip may engageat least one edge of the electronic board. In an embodiment, stiffenerssuch as tubes and/or external stiffening components may also limitflexibility of electronic boards and/or battery housings. For example,when an electronic board is potted inside a tube, a stiff pottingmaterial (e.g. an epoxy) may surround at least a portion of theelectronic board within the tube and limit deflection of the electronicboard. Bending a circuit board can stress the solder joints holding thecomponents causing them to fail. Direct acceleration of the board willalso result in inertial loads as the individual components resist thatmotion. The inertial loads can also damage the solder joints. Directacceleration of the components can also result in internal damage to theelectronic components. Similarly, acceleration and deformation ofbattery cells can result in leakage and internal damage that can degradeperformance. Sensitive components within pressure transducers oraccelerometers, such as MEMS silicon components, can also be damaged byhigh frequency acceleration above a threshold.

For some sensors, such as dynamic pressure transducers, a shockprotection apparatus may include a shock mitigating member disposedbetween at least one end of the sensor and a housing of a sensingsubassembly, where the shock mitigating member is configured to reducetransmission of a mechanical wave between the housing and the sensor.The shock protection apparatus may also comprise at least one sealmember disposed between the sensor and the housing. The shock protectionapparatus may protect a sensor from mechanical waves by attenuating someof the mechanical waves before the mechanical waves reach the sensor aswell as by reflecting some of the mechanical waves away from the sensor,all while permitting the sensor to be in fluid communication with anexterior of the housing.

For some electronic devices, such as electronic boards and batteries, ashock protection apparatus may include a stiffening member engaging anelectronic board, wherein the stiffening member is configured to limitat least high frequency mechanical waves communicated to the electronicboard and/or transform at least some of the high frequency mechanicalwaves into lower frequency motion or waves, thereby reducing the forceson the electronic board in the axial and radial directions along thesubassembly. The shock protection apparatus may also include a springstructure coupled to at least a portion of the electronic board andconfigured to limit deflection of the electronic board in the axial andradial directions along the axis of the subassembly. The springstructure may couple the electronic board with at least one cavity wallin the housing. This shock protection apparatus resists moments createdacross an electronic device from a mechanical wave so that, for example,solder joints on an electronic board are not broken during thedetonation of a perforating gun. Furthermore, this shock protectionapparatus may resist axial and radially deflection resulting from amechanical wave produced by the detonation of a perforating gun.

For some sensors, such as accelerometers, a shock protection apparatusfor use with a downhole tool may include at least one isolating memberdisposed within a cavity in a housing of a sensing subassembly. The atleast one isolating member may be configured to attenuate (e.g., absorband/or reflect) and/or convert at least a portion of frequencycomponents of a mechanical wave above a threshold and transmit at leasta portion of frequency components below the threshold to the sensor.This shock protection apparatus may also be configured to attenuate atleast a portion of the frequency components of a mechanical wave above athreshold produced by the detonation of perforating gun in at least onecoordinate axis, while at the same time transmit at least a portion ofthe frequency components below the threshold to the sensor. This mayallow the sensor to obtain an accurate reading of a desired frequencyrange while limiting interference from unwanted frequency componentsthat would potentially damage the sensor and hinder accurate sensorreadings.

Referring to FIG. 1, an example of a wellbore operating environment isshown. As depicted, the operating environment comprises a drilling rig100 that is positioned on the earth's surface 104 and extends over andaround a wellbore 114 that penetrates a subterranean formation 102 forthe purpose of recovering hydrocarbons. The wellbore 114 may be drilledinto the subterranean formation 102 using any suitable drillingtechnique. The wellbore 114 extends substantially vertically away fromthe earth's surface 104 over a vertical wellbore portion 116, deviatesfrom vertical relative to the earth's surface 104 over a deviatedwellbore portion 136, and transitions to a horizontal wellbore portion118. In alternative operating environments, all or portions of awellbore may be vertical, deviated at any suitable angle, horizontal,and/or curved. The wellbore may be a new wellbore, an existing wellbore,a straight wellbore, an extended reach wellbore, a sidetracked wellbore,a multi-lateral wellbore, and other types of wellbores for drilling andcompleting one or more production zones. Further, the wellbore may beused for both producing wells and injection wells. In an embodiment, thewellbore may be used for purposes other than or in addition tohydrocarbon production, such as uses related to geothermal energy.

A wellbore tubular string 120 comprising a shock protection apparatus150 may be lowered into the subterranean formation 102 for a variety ofworkover or treatment procedures throughout the life of the wellbore.The embodiment shown in FIG. 1 illustrates the wellbore tubular 120 inthe form of a workover string being lowered into the subterraneanformation. It should be understood that the wellbore tubular 120comprising a shock protection apparatus 150 is equally applicable to anytype of wellbore tubular being inserted into a wellbore, including asnon-limiting examples drill pipe, production tubing, rod strings, andcoiled tubing. In the embodiment shown in FIG. 1, the wellbore tubular120 comprising the shock protection apparatus 150 can be conveyed intothe subterranean formation 102 in a conventional manner.

The drilling rig 106 comprises a derrick 108 with a rig floor 110through which the wellbore tubular 120 extends downward from thedrilling rig 106 into the wellbore 114. The drilling rig 106 comprises amotor driven winch and other associated equipment for extending thewellbore tubular 120 into the wellbore 114 to position the wellboretubular 120 at a selected depth. While the operating environmentdepicted in FIG. 1 refers to a stationary drilling rig 106 for loweringand setting the wellbore tubular 120 comprising the shock protectionapparatus 150 within a land-based wellbore 114, in alternativeembodiments, mobile workover rigs, wellbore servicing units (such ascoiled tubing units), and the like may be used to lower the wellboretubular 120 comprising the shock protection apparatus 150 into awellbore. It should be understood that a wellbore tubular 120 comprisingthe shock protection apparatus 150 may alternatively be used in otheroperational environments, such as within an offshore wellboreoperational environment.

In alternative operating environments, a vertical, deviated, orhorizontal wellbore portion may be cased and cemented and/or portions ofthe wellbore may be uncased. For example, uncased section 140 maycomprise a section of the wellbore 114 ready for being cased withwellbore tubular 120. In an embodiment, a shock protection apparatus 150may be used on production tubing in a cased or uncased wellbore.

Representatively illustrated in FIG. 2 is a well system 10 which canembody principles of the present disclosure. In the well system 10, aperforating string 12 is installed in a wellbore 14. The depictedperforating string 12 includes a packer 16, a firing head 18,perforating guns 20, and a sensing subassembly 21. In other examples,the perforating string 12 may include more or less of these components.For example, well screens and/or gravel packing equipment may beprovided, any number (including one) of the perforating guns 20 andsensing subassemblies 21 may be provided, etc. Thus, it should beclearly understood that the well system 10 as depicted in FIG. 2 ismerely one example of a wide variety of possible well systems which canembody the principles of this disclosure.

One advantage of interconnecting the sensing subassembly 21 in closeproximity to the perforating guns 20 may be to allow for more accurateand reliable measurements of the parameters (e.g., strain, acceleration,pressures, temperatures, etc.) associated with a perforating event. Thesensors within a sensing subassembly 21 may also be used to detect andmeasure conditions in the wellbore 14 in close proximity to perforations24 immediately after the perforations are formed, thereby facilitatingmore accurate and reliable analysis of characteristics of an earthformation 26 penetrated by the perforations.

A sensing subassembly 21 comprising a shock protection apparatus 22 canbe disposed above the perforating guns 20, between two perforating guns20, and/or below the perforation guns 20. Regardless of the type ofenvironment the sensing subassembly 21 is used, it will be appreciatedthat a shock protection apparatus disposed within the sensingsubassembly 21 serves to protect an electronic device such as a sensorand/or electronics board from damage, for example due to a mechanicalwave generated during a perforating event. The sensing subassembly 21comprising a shock protection apparatus 22 may be interconnected abovean upper perforating gun 20 to more accurately and reliably record theforces and parameters resulting from a perforating event on theperforating string 12 above the perforating guns. The informationobtained from the sensors may be used to design the various componentsof the system to limit and/or prevent unsetting or other damage to thepacker 16, firing head 18, etc., due to detonation of the perforatingguns 20. In an embodiment, a sensing subassembly 21 interconnectedbetween perforating guns 20 may be used to detect the effects ofperforating on the perforating guns 20 themselves. In some embodiments,a sensing subassembly 21 may be connected below the lowest perforatinggun 20 to more detect and record the effects of perforating on anycomponent located below the perforating train. In some embodiments, theperforating string 12 could be stabbed into a lower completion string,connected to a bridge plug or packer at the lower end of the perforatingstring, etc., in which case the information recorded by a sensingassembly 21 may be used to detect the forces acting on the variouscomponents below the perforating guns 20.

Viewed as an overall system, a perforating string 12 comprising asensing subassembly 21, which in turn may comprise a shock protectionapparatus 22, may allow for the acquisition of data at various pointsbetween or near one or more perforating guns, which may be useful indeveloping and/or validating a model of the system. Thus, reliably andaccurately collecting data above, between and/or below the perforatingguns 20, for example, can help in an understanding of the overallperforating event and its effects on the system as a whole. The sensingassembly 21 comprising a shock protection apparatus 22 may moreaccurately and reliably obtain information not only useful for futuredesigns, but for current designs, for example, in post-job analysis,formation testing, etc. The applications for the information obtained bythe sensing assembly 21 are not limited at all to the specific examplesdescribed herein.

While described in terms of a sensing subassembly disposed in aperforating string, the sensing subassembly and shock protectionapparatus described herein may also be used with any number of othertools, such as drilling, completion, production, and/or workover tools.In an embodiment, the sensing subassembly may be disposed in a wellboretubular string, or the sensing subassembly may comprise a separatecomponent that is coupled or engaged to a wellbore tool (e.g., affixedto using any suitable connection mechanism) to measure one or moreparameters. For example, the sensing subassembly may be coupled to anoutside of a wellbore tubular tool or string, and/or the sensingsubassembly may be disposed in a recess or cavity on a wellbore tubularstring or tool.

In general, the shock protection apparatus 22 may be used to passivelyisolate one or more sensors within the sensing subassembly 21 using oneor more of a variety of techniques. For example, the shock protectionapparatus may comprise a sensor acting as a mass that may be coupledwithin the sensing subassembly using a spring and damping elements,which may be the same component. The sensor coupled in the sensingsubassembly by the spring and damping elements can be thought of asmoving as a harmonic oscillator. The characteristics of the mass and thespring stiffness can be used to determine a natural frequency of thesystem. Damping may dissipate energy in the system, which may reduce thevibration level which is transmitted at the natural frequency. Thecharacteristics of the damping element cause energy dissipation duringthe oscillation and have a secondary effect on the natural frequency.The shock protection apparatus may provide isolation for the sensor frommechanical waves in both directions, isolating the sensor fromvibrations traveling from the sensing subassembly, and also isolatingthe sensing subassembly from vibrations originating in the sensor.Moreover, the shock protection apparatus may provide isolation for thesensor from mechanical waves traveling in a plurality of directions andoriginating from a variety of sources.

When vibration is applied (e.g., due to a mechanical wave), energy canbe transferred more efficiently at the natural frequency as compared toabove or below the natural frequency. The efficiency and extent of theisolation a given situation may depend on a variety of factorsincluding, but not limited to, the frequency, direction, and magnitudeof vibrations present, the desired level of attenuation of thosefrequencies, and the characteristics of the components of the dampingsystem (e.g., the mass or sensor, the spring, and/or the dampingelements). As described in more detail herein, the shock protectionapparatus may be used to allow relative movement between the sensor andthe surrounding sensing subassembly in response to a mechanical wave.Due to the presence of the spring element and the damping element, therelative movement or motion is not free motion, but rather serves toisolate the sensor from the mechanical wave to at least some degree.

The properties of the shock protection apparatus may also be configuredto reduce the transmission of the mechanical wave, and may for examplereduce the mechanical wave above a threshold. The threshold mayrepresent an amplitude or a frequency threshold. For example, theproperties of the shock protection apparatus may be selected to allowcertain mechanical wave frequency ranges to be transmitted to the sensorwhile at least partially isolating mechanical wave frequency rangesabove a threshold. Isolation based on a threshold may be used toreducing the transmission of potentially harmful mechanical waveamplitudes or frequencies while allowing amplitude or frequency rangesof interest to be transmitted to the sensor for detection

Referring additionally now to FIGS. 2-4, one example of as sensingsubassembly 21 comprising a shock protection apparatus 22 isrepresentatively illustrated. As depicted in FIG. 3, the sensingsubassembly 21 is provided with mechanical end connectors 28 forinterconnecting the tool in the perforating string 12 in the well system10. The end connectors 28 may include both mechanical connections suchas threads for coupling the sensing subassembly with an adjacent tubularcomponent as well as one or more fluid and/or electrical connections forallowing a signal (e.g., an electrical signal, control signal, etc.) tobe transmitted through the sensing subassembly 21. In addition, othertypes of connectors may be used, and the shock protection apparatus 22may be used in other perforating strings and in other well systems, inkeeping with the principles of this disclosure.

In FIG. 4, it may be seen that four of the electrical connectors 50 areinstalled in a bulkhead 54 at one end of the sensing subassembly 21.While four electrical connectors 50 are shown, less than four or morethan four may be included as desired, and each electrical connector 50may comprise one or more electrical connections (e.g., pins, receivers,etc.). In an embodiment, a pressure sensor 56, a temperature sensor 58,and/or an accelerometer 60 can be mounted to the bulkhead 54. Thepressure sensor 56 can be used to monitor pressure external to thesensing subassembly 21, for example, in an annulus 62 formed radiallybetween the perforating string 12 and the wellbore 14 (see, for example,FIG. 2). The pressure sensor 56 may comprise any pressure sensorsuitable for use in a wellbore environment that is capable of measuringthe pressure within the sensing subassembly 21 and/or the wellbore. Thepressure sensor 56 may be configured to measure the static and/ordynamic pressure. A suitable pressure sensor 56 may include, but is notlimited to, Kulite model HKM-15-500 pressure transducer (available fromKulite Semiconductor Products, Inc. of Leonia, N.J.). The temperaturesensor 58 may be used for monitoring temperature within the tool 22and/or the wellbore. The accelerometer 60 may be used to measure thevarious movements and/or forces applied to the sensing subassembly 21.In an embodiment, the accelerometer 60 may comprise a piezoresistivetype accelerometer, although other types of accelerometers may be used,if desired. Suitable accelerometers may include, but are not limited to,a PCB 3501A series accelerometer (available from PCB of Depew, N.Y.),which is available in single axis or triaxial packages and is capable ofsensing up to 60,000 g acceleration.

In FIG. 5, a cross-sectional view of a sensing subassembly 21 with apressure transducer, electronic board, and an accelerometer isschematically illustrated. One or more electrical couplings (e.g.,electrical wires 818) may be used to electrically couple one or more ofthe components of the sensing subassembly 22. In this view, it may beseen that the sensing subassembly 21 may include a detonation train 30extending through the interior of the tool. The detonation train 30 cantransfer detonation between perforating guns 20, between a firing head(not shown) and a perforating gun, and/or between any other explosivecomponents in the perforating string 12. In the example of FIGS. 2-4,the detonation train 30 may include a detonating cord 32 and explosiveboosters 34, but other components may be used, if desired.

In an embodiment as shown in FIG. 6, a shock protection apparatus may beused to protect a sensor 508 exposed to the exterior of the sensingsubassembly 21. The shock protection apparatus 502 for use in a downholetool may be disposed in a sensing subassembly 500. The sensingsubassembly 500 generally comprises a housing 504 having a cavity 506extending into the housing 504. The sensing subassembly 500 may comprisea sensor 508 disposed at least partially within the cavity 506, where atleast a portion of the sensor 508 may be in fluid communication with anexterior of the housing 504. A mounting ring 524 may be disposed about aportion of the sensor 508 and serve to centralize the sensor 508 withinthe cavity 506 during use. A retaining ring 520 may be disposed betweenthe sensor 508 and the exterior to the housing 504. The retaining ring520 may engage the interior of the cavity 506 and serve to retain themounting ring 524, and thereby the sensor 508, within the cavity 506during use. A port may be disposed within the housing 504 to allow forone or more couplings from the sensor to pass through the housing 504 toanother component within the sensing subassembly 21 such as anelectronics board.

A shock protection apparatus 502 may be disposed between the sensor 508and the housing 504. The shock protection apparatus 502 comprises ashock mitigating member 510 disposed between at least one end of thesensor 508 and the housing 504. The shock mitigating member 510 may beconfigured to reduce transmission and/or attenuate at least a portion ofa mechanical wave traveling between the housing 504 and sensor 508. Theshock protection apparatus 500 may also include at least one seal 512disposed about the sensor 508 and between the sensor 508 and the housing504. In some embodiments, a seal may be disposed between the sensor 508and the mounting ring 524. In an embodiment, the seal 512 disposedbetween the sensor 508 and the mounting ring 524 may comprise a metalcrush ring and/or a dual o-ring geometry. In an embodiment, the sensor508 comprises a pressure sensor, such as a static and/or dynamicpressure sensor. In an embodiment, suitable pressure sensors may includethe Kulite HKM series for measuring both static and dynamic pressuresand the PCB 119B for measuring dynamic pressures. In some embodiments,various additional sensors such as strain gauges may also be used tomeasure pressure (e.g., static pressure). In an embodiment, the sensor508 may comprise a pressure sensor, a temperature sensor, a loggingsensor, and/or an optical sensor. In an embodiment the sensor 508 maycomprise any sensor used by one of ordinary skill in the art.

In an embodiment, the sensor 508 may be disposed in the sensingsubassembly 500 so that at least a portion of the sensor 508 may be influid communication with an exterior of the housing 504. For example,the sensor 508 may be disposed so that a sensing face 514 is in fluidcommunication with an exterior of the housing 504. When the sensor 508is disposed so that sensing face 514 is in fluid communication with anexterior of the housing, the sensor 508 may detect changes in pressurecaused by a pressure wave moving along the wellbore. For example, thesensor may measure a dynamic pressure from a pressure wave resultingfrom the detonation of a perforating gun. In another embodiment, thesensor 508 may detect static pressure at the exterior of the housing504.

In an embodiment, the sensor 508 may be positioned within the housing504 close to the outer surface of the housing 504 so that any cavityresonance is minimized. In this embodiment, the longitudinal axis of thesensor 508 may be oriented about ninety degrees from the wellboretubular longitudinal axis (e.g., the sensor axis may be orientedperpendicular to the longitudinal axis of the wellbore tubular) so thatany cavity resonance is minimized while allowing a pressure signal to bedetected and measured. In an embodiment, when the sensor 508 is orientedat about ninety degrees from the wellbore tubular axis, the electricalconnections (e.g., the wires) may be disposed substantially parallelwith the wellbore tubular axis through the housing 504.

In some embodiments, the sensor 508 may have a length that prevents itfrom being oriented at about ninety degrees from the wellbore tubularaxis. In this case, the sensor 508 may need to be disposed at an angleless than ninety degrees relative to the wellbore tubular axis whilestill allow the sensor 508 to have a sensor face close to the exteriorof the housing 504. The sensor 508 may be at least partially disposed ina flow path that provides fluid communication through the housing 504between the sensor 508 and the exterior of the housing 504. The flowpath may comprise a bore that is disposed at an angle between about zerodegrees and about 90 degrees with the wellbore tubular axis. The flowpath may comprise one or more legs to provide the appropriate spacingfor the sensor and/or any communication components (e.g., electricalconnections, wires, etc.). One of ordinary skill in the art willappreciate that a plurality of sensor types may be disposed in thehousing. Additionally, one of ordinary skill in the art will appreciatethat when a sensor, such a static pressure transducer, is recessed inthe housing 504 and a flow path provides fluid communication between theexterior of the housing 540 and the sensor 508, the sensor 508 may sensea parameter, such as static pressure, at the exterior of the housing viathe flow path. In an embodiment, the sensor 508 may be recessed withinthe housing 504 away from the outer surface of the sensing subassembly500, for example, to protect the sensor 508 and/or so that sensor 508can be positioned in close proximity to supporting electronics.

The sensor may also detect the dynamic and/or static pressure within aportion of the housing (e.g., in an internal flowbore, etc.). In anembodiment, the flow path may be configured to provide fluidcommunication between a sensor 508 and an internal fluid pathway withinthe wellbore tubular. For example, a detonation cord housing may not beloaded with a detonation cord so that an internal fluid pathway maycommunicate through the detonation cord housing for a variety of wellcompletion operations. Fluid communication may be established betweenthe detonation cord housing and the sensor to sense one or moreparameters, such as pressure, temperature, flow rate, etc., within theinterior of the housing.

In an embodiment, a screen 516, can optionally be disposed over at leasta portion of the sensor 508 between the sensor 508 and the exterior ofthe housing 504. As shown in FIG. 6, the screen 516 may be disposed overat least a portion of the sensing face 514. In an embodiment, the screen516 is configured to protect the sensing face 514 from debris that maybe present in the wellbore. When the screen 516 is disposed on at leasta portion of the sensing face 514, the screen 516 may protect thesensing face 514 from damaging contact from debris when impacted by amechanical wave.

In an embodiment, an optional coating composition 518, may be disposedover at least a portion of the sensor 508. The coating composition 518may be disposed on at least a portion of the sensing face 514. When ascreen 516 is present, the coating composition 518 may be disposedbetween the sensing face 514 and the screen 516 and/or on the outside ofthe screen 516. In an embodiment, the coating composition 518 maythermally insulate the sensor 508 from the exterior of the housing 504.When the coating composition 518 is disposed on at least a portion ofthe sensing face 514, the coating composition 518 may thermally insulatethe sensor face 514 from the heat generated by the detonation of aperforating gun.

In an embodiment, an electrical insulator may be disposed between thesensor 508 and the housing 504 and/or the mounting ring 504. Anelectrical insulator may also be disposed between the mounting ring 524and the housing 504. The electrical insulator may be configured tomanage electrical noise during a wellbore operating procedure. Forexample, when a perforating gun is detonated within a wellbore, thesensor 508 may sense, for example, a pressure change, within thewellbore. As the sensor 508 converts the pressure signal into anelectrical signal and sends the electrical signal to supportingelectrical components, the signal may be distorted due to contact withelectrically conductive components surrounding the sensor 508 creatingunwanted electrical noise. Disposing an electrical insulator between thesensor 508 and other components of the shock protection apparatus 500may mitigate electrical noise interfering with sensor signals.

The retaining ring 520 may be disposed between the sensor 508 and theexterior of the housing 504. In an embodiment, the retaining ring 520may be pinned to and/or threadedly engaged with the wall of the cavity506 and/or the housing 504. When the retaining ring 520 is disposedbetween the sensor 508 and the exterior of the housing 504, theretaining ring 520 may be configured to provide a compression force onthe shock isolation member 510. For example, the retaining ring 520disposed between the sensor 508 and the exterior to the housing 504 mayprovide a compression force on the mounting ring 524, which may in turnprovide a compression force on the shock isolation member 510, beforethe sensing assembly 500 is disposed in a wellbore. The retaining ring520 may also prevent the sensor 508 from displacing out of the cavity506 of the housing 504 during the detonation of a perforating gun.

In an embodiment, at least one washer 522 may be disposed between theretaining ring 520 and the mounting ring 524 and/or the sensor 508. Inan embodiment, the washer 522 may be configured to attenuate a portionof the pressure wave above a threshold isolation frequency. In anembodiment, the washer may comprise an elastomeric washer. In anembodiment, the washer 522 may support and isolate the sensor 508 alongthe axis of the sensor 508 from deflections caused by the detonation ofa perforating gun. The washer 522 may comprise a relatively softermaterial (e.g., softer than the material of other members such as theretaining ring 520, the mounting ring 524, and/or the housing 504). Therelatively softer material of the washer(s) 522 may provide more shockisolation. The softer material of the washer(s) 522 may also providecompliance for torqueing the retaining member 520 when pre-loading thesensing subassembly 500. In an embodiment, the effective axial and shearstiffness of the washer 522 can be tuned to achieve a desirableisolation frequency for shock protection. As an alternative to a washerand/or an elastomeric washer, the washer 522 may comprise a wave springand/or a Belleville type spring. To that effect, a wave spring and/or aBelleville type spring may be used in conjunction with a washer and/oran elastomeric washer.

In an embodiment, an additional washer similar to the washer 522 may bedisposed between the mounting ring 524 and the shock mitigating member510. The washer may comprise an elastomeric washer. The washer may beconfigured so that at least a portion of the sensor 508 is in fluidcommunication with an exterior of the housing 504 and the washer 522 canprovide support and isolation for the sensor 508 along the axis of thesensor 508. In an embodiment, the washer may provide radial support andisolation for the sensor 508 about the axis of the sensor 508. Forexample, the washer may abut the sensor 508 to provide shear supportand/or radial isolation for the sensor 508. The washer may be subject tohydrostatic loads and may have a sufficiently high compressive strengthto avoid deflection and/or damage to the sensor 508 and the mountingring 524.

The mounting ring 524 may be disposed about the axis of the sensor 508between the shock mitigating member 510 and the washer 522. In anembodiment, the mounting ring 524 may be configured so that at least aportion of the sensor 508 is in fluid communication with an exterior ofthe housing 504. The mounting ring 524 may provide support and isolationfor the sensor 508 along the axis of the sensor 508 and/or radiallyabout the axis of the sensor 508. In an embodiment, the mounting ring524 may be coupled to the sensor 508 for added leak protection (e.g.,welded to the sensor, integrally formed with the sensor, etc.). Themounting ring 524 may also be configured so that at least one sealmember 512, at least one seal back up 530, a washer 522, and/or areflection member 510 may prevent the mounting ring 524 from engagingthe cavity wall. When the mounting ring 524 is isolated from the cavitywall and the interfacing components are electrically insulating,substantial electrical isolation may be achieved for electromagneticsignal transmission through the sensor 508.

One or more seal member housings 528 may be circumferentially disposedabout the mounting ring 524 and/or the sensor 508. In an embodiment, atleast one seal member housing 528 may be configured to support at leastone seal member 512. The at least one seal member housing 528 maycomprise a groove disposed on the outside diameter of the mounting ring524 and/or the sensor 508. In an embodiment, a first and a second sealmember housing 528 may be circumferentially disposed about the mountingring 524 and/or sensor 508. In an embodiment, the at least one sealmember housing 528 may be configured to support at least one seal member512 and/or at least one seal back up member 530.

At least one seal member 512 may be disposed in the seal member housing528 between the sensor 508 and the housing 504. In an embodiment, atleast one seal back up member 530 may be disposed adjacent to the atleast one seal member 512 within the at least one seal member housing528. The at least one seal member 512 and/or the at least one seal backup member 530 may sealingly engage the housing 504 and seal at least aportion of the sensor 508 as well as the wire 526 to prevent fluidcommunication with the exterior of the housing 504. In an embodiment,the at least one seal member 512 and/or the at least one seal back upmember 530 may serve to isolate at least a portion of a mechanical wavetraveling between the mounting ring 524 and the housing 504. In anembodiment, the at least one seal member 512 and the at least one sealback up member 530 may serve to isolate at least a portion of acompression wave function traveling along the axis of the sensor 508. Inan embodiment, when at least one seal member 512 is disposed about theaxis of the sensor 508 between the sensor 508 and the housing 504, theat least one seal member 512 may contact the housing 504 and may serveto isolate at least a portion of a compression wave traveling betweenthe mounting ring 524 and/or the sensor 508 and the housing 504.

The at least one seal member 512 and/or the at least one seal back upmember 530 may be subject to hydrostatic loads. In an embodiment, the atleast one seal member 512 and/or the at least one seal back up member530 may comprise suitable elastomeric compounds which may include, butare not limited to, ethylene propylene diene monomer (EPDM),fluoroelastomers (FKM) [Viton®], perfluoroelastomers (FFKM) [Kalrez®,Chemraz®, Zalak®], flouoropolymer elastomers [Viton®],polytetrafluoroethylene, copolymer of tetrafluoroethylene and propylene(FEPM) [Aflas®], and polyetheretherketone (PEEK), polyetherketone (PEK),polyamide-imide (PAI), polyimide [Vespel®], polyphenylene sulfide (PPS),and any combination thereof. In an embodiment, at least one seal member512 may be disposed about the axis of the sensor 508 and may not requirethe support of an at least one seal member housing 528 or a mountingring 524. In an embodiment, at least one seal back up member 530 may bedisposed about the axis of the sensor 508 and may not require thesupport of an at least one seal member housing 528 or a mounting ring524. When a seal member 512 is disposed about the axis of the sensor 508between the sensor 508 and the housing 504, the seal member 512 maysealingly engage the housing 504 and substantially prevent fluidcommunication from the exterior of the housing past the seal member 512.

In an embodiment, an optional elastomer 534 may be disposed on at leasta portion of the wall of the cavity 506. The elastomer 534 may comprisea material configured to minimize lateral motion of the sensor 508 whenimpacted by a pressure wave. The elastomer 534 may be disposed around aportion of the wall of the cavity 506 adjacent to the sensor 508 and thewiring 526. The elastomer 534 may also be configured to reduce thedeflection of the sensor 508 and the wiring 526. In an embodiment, theelastomer 534 may also coat the cavity 506 so that if a fluid enters thecavity, the elastomer 534 may protect the housing 504 from the fluid. Inan embodiment, when an elastomer 534 is disposed on at least a portionof the wall of the cavity 506, the elastomer 534 provides a sealprotecting the housing 504 from fluid that may form or seep through theseal member 512.

In an embodiment, a pocket 536 disposed in the housing comprises atleast one compressible component (e.g., foam, a compressible fluid, aporous elastomer, etc.) and is disposed between at least a portion ofthe sensor 508 and at least a portion of the housing 504. The at leastone pocket may be is disposed between the housing 504 and portion of thesensor 508 and the wiring 526. In an embodiment, the at least one pocket536 may be encapsulated and/or retained by an encapsulant and/or a foamabutting the elastomer 534 and/or disposed between the between at leasta portion of the sensor 508 and at least a portion of the housing 504.When the apparatus 500 experiences a pressure wave, a compressiblecomponent (e.g., foam) disposed within a pocket 536 may providecompressibility for the elastomer 534. The at least one pocket 536comprising at least one compressible component may also dampendeflection of the sensor 508 and the wiring 526 in conjunction with theelastomer 534.

As disclosed in FIGS. 7A and 7B, a shock mitigating member 510 may bedisposed between at least one end of the sensor 508 and the housing 504.The shock mitigating member 510 is generally disposed about the axis ofthe sensor 508 and in contact with the mounting ring 524 on one end andthe housing 504 on the opposite end. The end of the shock mitigatingmember 510 engaging the housing may engage a shock mitigating memberseat 532 formed in the housing 504. In an embodiment, the shockmitigating member 510 may be disposed adjacent to at least one sealmember 512 and/or at least one seal back up member 530. In anembodiment, the shock mitigating member 510 may be in the location ofthe washer 522 disclosed in FIG. 6 and/or the washer 522 may be in thelocation of the shock mitigating member 510. In an embodiment, the shockmitigating member 510 is subject to hydrostatic loads. The shockmitigating member 510 may provide mechanical wave reflection,attenuation, and/or transmission away from the sensor 508 and/orelectrical components. For example, when the sensor 508 experience amechanical wave and/or pressure disturbance, the shock mitigating member510 may protect the sensor and/or the electrical components, includingthe electrical wires, from damage and/or distortion. In an embodiment,the shock mitigating member 510 may have a sufficiently high compressivestrength to limit or avoid deflection and/or damage to the sensor 508,the mounting ring 524, and/or the wires 526 disposed behind and attachedto the sensor 508. In an embodiment, the wires 520 may be coupled to anon-transitory computer readable media 536 for receiving a signal fromthe sensor 508.

FIGS. 7A and 7B illustrate additional views of the shock protectionapparatus 502. The shock mitigating member 510 comprises at least twoengaging shock mitigating sections 602 and 604. The at least two shockmitigating sections 602, 604 are disposed about the sensor 508 and incontact with each other. The shock mitigating sections 602, 604generally comprise different materials. For example, the first shockmitigating section 602 comprises a first material and the second shockmitigating section 604 comprises a second material. The use of differentmaterials may provide for an impedance mismatch, thereby reflecting atleast a portion of a compression wave incident on the shock mitigatingmember 510. For example, the first material may comprise a firstimpedance and the second material may comprise a second impedance suchthat the impedance of the first material and thus the impedance of firstshock mitigating section 602 is different from the impedance of thesecond material and thus the impedance of the second shock mitigatingsection 604. In an embodiment, the material of the first shockmitigating section 602 may comprise a metal such as aluminum and thesecond shock mitigating section 604 may comprise a polymer such as PEEK.In an embodiment, the ratio between the impedance of the first materialand the impedance of the second material is greater than 1.1. In anembodiment, the impedance of each of the shock mitigating sectionscomprises a mechanical/acoustic impedance.

In an embodiment, when the shock mitigating member 510 is disposed aboutthe axis of the sensor 508 between at least one end of the sensor 508and the housing 504, the shock mitigating member 510 may reduce thetransmission of at least a portion of a pressure wave produced by thedetonation of a perforating gun to the sensor 508. Specifically, theshock mitigating member 510 may allow transmission of the pressure waveinto and through, for example, the first shock mitigating members 602with a first impedance. When the mechanical wave travels through thefirst shock mitigating component 602 with the first impedance andimpacts the interface between the first shock mitigating section 602 thesecond shock mitigating section 604 having a second impedance, thechange in impedance between the first reflective section 602 and thesecond reflective section 604 causes at least a portion of the pressurewave to reflect off of the interface, thereby reducing the transmissionof the pressure wave to the sensor 508.

The shock mitigating member 510 may comprise a plurality of shockmitigating sections. In this embodiment, no two shock mitigatingsections in contact with each other may have the same impedance. Thus,for example, the first shock mitigating section 602 may not make contactalong the axial direction of the sensor 508 with another shockmitigating section with the same impedance as the first shock mitigatingsection 602. In an embodiment, a sufficient number of shock mitigatingsections may be used to fill any space between the mounting ring 524 andthe housing 504. In an embodiment, spacers may be disposed between atleast two of the shock mitigating sections of the shock mitigatingmember 510 so that the shock mitigating sections may be retained incompression. Additionally, spacers may be provided so that the shockmitigating member 510 may be retained in compression in conjunction withat least one other component of the shock protection apparatus 500. Inanother embodiment, the retaining member 520 may be torqued usingthreads to provide the compression without the use of spacers on shockmitigating sections and/or between the shock mitigating member 510 andanother component of the shock protection apparatus 502.

In an embodiment, at least two adjacent engaging shock mitigatingsections of the plurality of shock mitigating sections may provide anacoustic impedance mismatch, such that pressure wave energy incident onthe shock mitigating section is partly reflected at the interfacebetween adjacent sections, thereby attenuating the pressure wave energytraveling through the sections. A variety of methods of implementingthis impedance mismatch are consistent with the present disclosure. Forexample, an impedance mismatch may be achieved by rapidly changingcross-section or density of the spacer relative to the remainder of theperforation tool assembly.

The shock mitigating member 510 may serve to attenuate mechanical wavecontent above an isolation frequency while allowing lower frequencies topass through. In an embodiment, the effective axial and shear stiffnessof the shock mitigating member 510 can be tuned to achieve a desirableisolation frequency for protection from mechanical waves. In anembodiment, the shock mitigating member 510 is configured to reducetransmission of a mechanical wave between the housing 504 and the sensor508. In an embodiment, the shock mitigating member 510 may be configuredto mitigate and/or reflect at least 5% of the pressure wave travelingbetween the housing 504 and the sensor 508. In an embodiment, the shockmitigating member 510 may be configured to mitigate and/or reflect atleast about 10%, at least about 15%, at least about 20%, at least about25%, at least about 30%, at least about 35%, at least about 40%, atleast about 45%, or at least about 50% of the pressure away travelingbetween the housing 504 and the sensor 508. In an embodiment in whichthe sensor 508 comprises a pressure sensor, the isolation frequency maybe about 1 kHz and/or above about 1 kHz. However, isolation may beconstrained by the required seal geometry and maximum allowabledeflection under hydrostatic pressure.

In an embodiment, a method of measuring a shock mechanical in a wellborecomprises disposing a sensing subassembly 500 comprising a sensor 508and a shock protection apparatus 502 into a wellbore, where the sensingsubassembly 500 comprises a housing 504 with a cavity 506 extending intothe housing 504, and a sensor 508 disposed at least partially within thecavity 506. The shock protection apparatus 502 may comprise a shockmitigating member 510 disposed between at least one end of the sensor508 and the housing 504. The sensing subassembly 500 may then receive atleast one mechanical wave (e.g., a shock wave, etc.) within thewellbore. The mechanical wave transmission to the sensor 508 may then bereduced using a shock mitigating member 510. A least one parameterassociated with the pressure wave can then be sensed before, during,and/or after a perforating event. The at least one parameter maycomprise a change in dynamic pressure. The sensor 508 may generate atleast one signal in response to the sensing and at least one signal canbe transmitted to and stored in a non-transitory computer readable media536. In an embodiment, the at least one pressure wave comprises adetonation mechanical wave generated by at least one perforating gundisposed within the wellbore.

In an embodiment, a method of absorbing at least a portion of amechanical wave using a shock protection apparatus comprises at leastone sensor 508 receiving a pressure wave disposed within a cavity 506 ofa housing 504, where the at least one sensor 508 is coupled to thehousing 504 at a first end via a shock mitigating member 510. A shockmitigating member 510 reflects and/or mitigates at least a portion ofthe pressure wave. The shock mitigating member 510 may also provideshock isolation by creating a softer support between the sensor 508 andthe housing 504. The shock mitigating member 510 may comprise a materialthat is softer than the sensor 508 and the housing 504. The reflectionof the pressure wave may include the transmission of a mechanical wavethrough a first material and onto a second material adjacent to thefirst material, where the first material and the second material aredisposed about the axis of the sensor 508. In an embodiment, the firstmaterial and the second material are adjacent to the housing. At leastone sensor 508 then senses at least one parameter external to thehousing.

In an embodiment, a method of absorbing at least a portion of amechanical wave using a shock protection apparatus further comprisesusing at least one washer 522 disposed adjacent to the sensor 508 andalong the axis of the sensor to attenuate at least a portion of themechanical wave. In an embodiment, at least one washer 522 attenuating amechanical wave may be compressed radially. A seal member 512 may bedisposed between the sensor 508 and the housing 504, and the seal member512 may attenuate a mechanical wave by allowing an axial deflectionalong the axis of the sensor 508 and/or a radial deflection along theaxis of the sensor 508 to thereby provide relative movement between thesensor 508 and the housing 504. Such relative motion may at leastpartially isolate the mechanical wave (e.g., attenuate the mechanicalwave). In an embodiment, at least one pocket comprising at least onecompressible component may be disposed between at least a portion of thesensor 508 and at least a portion of the housing 504, which may aid inallowing the compressible component to provide a soft support behind thesensor 508. The at least one pocket comprising the compressiblecomponent may alternatively and/or additionally provide a soft isolationmount for the back end of the sensor and/or the wiring. In anembodiment, the sensor 508 may be coupled to the housing 504 at a secondend by means of at least one washer 522. In an embodiment, the sensor508 is retained within the cavity 506 extending through the housing 504by a retaining ring 520 disposed between the sensor 508 and an openingof the cavity 506. The sensor 508 may comprise a dynamic pressuretransducer, a pressure sensor, a temperature sensor, a logging sensor,and/or an optical sensor.

In an embodiment, a shock protection apparatus may be used to protectelectronic boards and/or batteries. In FIG. 8, another cross-sectionalview of a sensing subassembly 800 is representatively illustrated. Thesensing subassembly 800 for use in a downhole tool may generallycomprises a housing 804 and a cavity 806. An electronic board 808 may bedisposed within the cavity 806. A shock protection apparatus 802generally comprises a stiffening member and a spring member 822. Theshock protection apparatus 802 may be configured to limit deflectionand/or flexing of the electronic board 808 along the axis of the sensingsubassembly 800 and radially about the axis of the subassembly 802. Inan embodiment, the shock protection apparatus 802 may also comprise atubular member 816, a polymeric material 812, and an isolation mount814.

In an embodiment, the electronic board 808 is disposed in the cavity 806of the housing 804 at an angle that is generally parallel to the axis ofthe subassembly 802. Due to the spatial constraints within the housing804, the cavity 806 may be sized so that the electronic board 808 fitssecurely within the cavity 806 and configured so that the electronicboard 808 does not interfere with, for example, the detonation cord 30(depicted in FIG. 5) while still shielding the electronic board 808 fromthe exterior of the housing 804. In an embodiment, the electronic board808 may be disposed so that the primary face of the electronic board 808faces inwards or outwards. In an embodiment, the electronic board 808may be disposed at a non-perpendicular angle relative to thelongitudinal axis of the sensing subassembly 800. The electronic board808 and the cavity 806 may be arranged so that the electronic board 802is able to fit securely within the sensing subassembly 800 and reducethe transmission of a mechanical wave produced, for example, from thedetonation of a perforating gun. In an embodiment, the at least oneelectronic board 808 may be disposed so that the electronic board 808 isnot in fluid communication with (e.g., is substantially fluidly isolatedfrom) an exterior of the housing 504.

In an embodiment, a stiffening member 809 may engage the electronicboard 808 and be configured to limit flexing of the electronic board808. In an embodiment, the stiffening member 809 may be used without anyother stiffening component such as a tubular member 816. In someembodiments, a combination of both a stiffening member and a tubularmember 816 may be used. In an embodiment, the shock protection apparatus800 may comprise the stiffening member engaged to each end of theelectronic board 808 (e.g., such as a stiffening strip 810 disposedalong an end of the electronic board 808). In an embodiment, astiffening member 809 may comprises a first stiffener disposed on atleast a first side of the electronic board and a second stiffenerdisposed on at least a second side of the electronic board. In someembodiments, at least one stiffening member 809 may engage at least oneside of the electronic board 808. For example, the stiffening member 809may be disposed along a side aligned with the longitudinal axis of theelectronic board 808 and/or a side perpendicular to the longitudinalaxis of the electronic board 808 (e.g., as illustrated by stiffeningstrip 810 in FIG. 8). In an embodiment, the stiffening member 809comprises a metal or composite beam engaged to at least one side of theelectronic board 808. The stiffening member 809 may be configured toresists moments that form across an electronic board 808 when acompression wave is transmitted to the electronic board 808. Thisfeature may reduce stress across solder joints and the other variouscomponents disposed on the electronic board 808 to maintain thefunctionality and prolong the life of the electronic board 808.

The stiffening member 810 may also be surrounded by (e.g., staked and/orpotted in) a polymeric material 812. As shown in FIG. 8, the polymericmaterial 812 may surround a least a portion of the electronic board 808.In an embodiment, the polymeric material 812 may stake the electronicboard to protect components on the electronic board. In an embodiment,the electronic board 808 may be potted and/or encapsulated in thepolymeric material 812. Furthermore, in an embodiment, the electronicboard 808 may be potted and/or encapsulated in the polymeric material812 within a tubular member 816, to be discussed in more detail herein.The polymeric material may provide heat dissipation on the electronicboard 808. The polymeric material 812 may be configured to providesupport to at least one electronic component on the electronic board 808and provide a shear coupling between the electronic board 808 and thecavity 806, or the electronic board 808 and the tubular member 816. Thepolymeric material 812 may also be configured to provide a secondaryload path and support for at least one solder joint on the electronicboard 808. The polymeric material 812 may also at least partially reactto inertial loads on the electronic board 808 and provide support to theelectronic components disposed thereon. In an embodiment, when apolymeric material 812 is disposed on at least a portion of theelectronic board 808, the polymeric material 812 may reduce and/or limitflexing of the electronic board 808 along the axis of the subassemblyand radially about the axis of the subassembly 802. For example, flexingmay be produced by a mechanical wave traveling through the sensingsubassembly 800 due to a mechanical wave. When a polymeric material 812is disposed on at least a portion of at least one electronic wireextending from the electronic board 808, the polymeric material 812 maysupport and protect the electronic wiring 818 from damage due to amechanical wave. Dampening and/or limiting the motion of the wiringsubject to a pressure wave may also minimize electronic noise that mayinterfere with a signal from a sensor and/or being processed on theelectronic board. In an embodiment, an isolation frequency of about 1kHz may be desired for the electronic board 808 and the wiring 818. Insome embodiments, a frequency of 1 kHz or greater may be reduced (e.g.,a frequency between about 1 kHz and about 100 kHz).

In an embodiment, the shock protection apparatus 802 may comprise atubular member 816. The tubular member 816 may be disposed about atleast a portion of the electronic board 808 and may be configured tolimit flexing of the electronic board 808 along the axis of thesubassembly and radially about the axis of the subassembly 802. In anembodiment, the tubular member 816 may be configured to be electricallyconnected to a ground reference on the board to minimize electromagneticnoise and interference. In an embodiment, the tubular member 816 may bedisposed within the cavity 806. The polymeric material 812 may serve tocouple the tubular member 816 to the electronic board 808. As disclosedin FIG. 8, the tubular member 816 may extend through at least a portionof the cavity 806 of the housing 804. The tubular member 816 may beconfigured to contain the electronic board 808.

As illustrated in FIGS. 9A-9C, the tubular member 816 may have ahexagonally shaped cross-section. In some embodiments, the cross-sectionof the tubular member 816 may comprise an oval shape, a polygonal shape,a circular shape, or a non-circular shape. In an embodiment, thecross-section of the tubular member 816 may comprise an open shape(e.g., a non-closed cross-sectional shape) having one or more openingsalong the cross section such as a c-shape, partial oval shape, partialnon-circular shape or the like. The shape of the tubular member 816 maybe configured (e.g., in size and/or in shape) to fit securely within thecavity 806 of the housing 804 of the sensing subassembly 800 whileallowing for the inclusion of the additional structures within thesensing subassembly 800 such as a detonation cord and the like. Theshock protection apparatus 802 may also comprise a material layer 820.The material layer 820 may be disposed on at least a portion of at leastone side of the electronic board 808, as disclosed in FIGS. 9A-9C. Forexample, the material layer may be disposed on one or more componentsbetween the one or more components and the potting and/or polymericmaterial. The material layer 820 may be configured to provideflexibility and/or compliance around the sensitive components of theelectronic board 808 to protect the sensitive components from thermalexpansion and/or shrinkage of the polymeric material. In an embodiment,the material layer 820 may be disposed over at least one primary face ofthe electronic board 808, which may comprise the face with the mostelectronic components. In an embodiment, the primary face of theelectronic board 808 may comprise a face comprising fragile components.The material layer 820 comprises a softer material than the polymericmaterial 812, and in an embodiment, may be a conformal coating. Thematerial layer 820 may be disposed over at least one solder jointdisposed on the face of the electronic board 808. When a material layer820 is disposed over at least a portion of at least one side of anelectronic board 808, the material layer 820 may provide support andstrength for at least one solder joint disposed on at least one side ofthe electronic board when the electronic board is exposed to a pressurewave, such as during a perforating event.

The shock protection apparatus 802 may further comprise a spring member822 coupling the electronic board 808 and/or the tubular member 816 tothe inner walls of the cavity 806. A pocket 826 may be disposed betweentwo portions of the spring member 822 to allow independent movement ofeach portion. The spring member 822 may be configured to provide anisolation mount reducing transmission of compression waves and/or thelimiting the amplitude of any compression waves transmitted to theelectronic board 808 through the shock protection apparatus 802. Thespring member 822 may be configured to limit the maximum deflection ofthe electronic board 808 and limit or prevent contact between theelectronic board 808 and other surrounding surfaces. Additionally, thespring member 822 may be configured to protect any electronic wires fromflexing and/or stretching. In an embodiment, the spring member 822 maybe configured to reduce or attenuate mechanical wave transmission aboveabout 500 Hz. The spring member 822 may be disposed around theelectronic board 808 and/or the stiffening member 809, and the springmember 822 may couple the electronic board 808 with at least one wall ofthe cavity 806. The spring member 822, in an embodiment, may be engagedwith at least a portion of a tubular member 816 retaining the electronicboard 808. In an embodiment, the spring member 822 may be configured tolimit deflection of the electronic board 808 along the axis of thesubassembly and radially about the axis of the subassembly 802. In anembodiment, the polymeric material 812 may be disposed on at least aportion of at least one electronic wire 818 (as shown in FIG. 5)extending from the electronic board 808 to support the electronic wire818 from deflection and damage from mechanical waves during detonationof a perforating gun.

In an embodiment, the polymeric material 812 may extend over the boardand serve the function of the spring member 822, potentially replacingthe spring member 822 if the spring member 822 is not present. Forexample, the subassembly 802 may not comprise the tubular member 816 sothat the polymeric material 812 provides the function of the springmember 822.

In an embodiment, a first spring member 822 comprising an elastomer maybe disposed at a first end of the cavity 806 and a second spring member824 comprising an elastomer may be disposed at a second end of thecavity 806. As disclosed in FIG. 8, the first spring member 822 may bedisposed over a portion of the electronic board 808 at a first end ofthe electronic board 808 and the second spring member 824 may bedisposed over at least a portion of the electronic board 808 at a secondend of the electronic board 808. The first spring member 822 and/or thesecond spring member 824 may retain the electronic board 808 in thecavity 806. The first spring member 822 disposed at a first end of thecavity 806 may be configured to engage at least a portion of the cavity806 and at least a portion of the polymeric material 812, and the secondspring member 824 disposed at a second end of the cavity 806 may beconfigure to engage at least a portion of the cavity 806 and at least aportion of the polymeric material 812. The first spring member 822 mayalso be configured to engage at least a portion of the tubular member816, and the second spring member 824 may be configured to engage atleast a portion of the tubular member 816. In an embodiment, a firstelastomer 822 disposed at a first end of the cavity 806 may attenuate atleast a portion of the mechanical waves across the electronic board 808.In an embodiment, a second elastomer 824 disposed at a second end of thecavity 806 may attenuate at least a portion of the mechanical wavesacross the electronic board 808.

The first spring member 822 and second spring member 824 may beconfigured to limit deflection of the tubular member 816, and therebythe electronic board 808, in the axial and radial directions along theaxis of the subassembly 802. The pocket 826 or void may be disposedbetween the first spring member 822 and the second spring member 824. Inan embodiment, an elastomer or a foam may be disposed in the pocket 826between the first spring member 822 and the second spring member 824.The material in the pocket 826 may be used to aid in manufacturing theshock protection apparatus 802 by providing the desired spacing betweenspring member 822, 824 during installation.

In an embodiment, one or more electronic connections 818 (e.g., a wire)may be coupled to the electronic board 808 to allow communicationbetween various components such as sensors and the electronic board 808.The first spring member 822 and/or the second spring member 824 mayencapsulate at least one wire 818 extending from the electronic board808. The at least one wire 818 extending from the electronic board 808,which may be encapsulated by the first spring member 822 and/or thesecond spring member 824, may be coiled or formed in a spiral or helicalconfiguration. The first spring member 822 and/or the second springmember 824 may be configured to limit deflection in the axial and radialdirections along the axis of subassembly of at least one wire extendingfrom the electronic board. The first spring member 822 and the secondspring member 824 may limit deflection of the electronic board 808and/or the wiring 818 engaging the electronic board 808 caused by amechanical wave impacting the sensing subassembly 800. For example, thefirst elastomer 822 and/or the second elastomer 824 may be configured tosupport at least one electronic wire 818 engaging the electronic board808 so that the at least one electronic wire 818 may not be damaged,broken, and/or disengaged from the electronic board during thedetonation of a perforating gun. In an embodiment, coiling and/orencapsulating at least one electronic wire 818 within at least the firstelastomer 822 and/or the second elastomer 824 may serve to attenuate amechanical wave incident on the electronic board that propagates to theelectronic wire 818 and/or causes relative motion between the electronicboard and the electronic wire 818.

While the spring members 822, 824 are illustrated as filling portions ofthe cavity 806, the spring member may also take the form of an isolationmount disposed between the electronic board 808 and the stiffeningmember 810. For example, the isolation mount may comprise a mechanicalspring and/or a damper arrangement, such as, for example, a coil springor a flexure encapsulated in rubber. In an embodiment, the isolationmount may comprise of a spring on each end of the electronic board 808and/or radial o-rings. In some embodiments, the spring members 822, 824may not be present and/or may be integrally formed with the polymericmaterial 812. In this embodiment, the polymeric material 812 may extendover the board and serve the function of the spring member 822,potentially replacing the spring member 822 if the spring member 822 isnot present. For example, the subassembly 802 may not comprise thetubular member 816 so that the polymeric material 812 provides thefunction of the spring member 822.

In an embodiment, a material layer 820 may be disposed over at least aportion of at least one face of the electronic board 808 to attenuatethe mechanical wave. The material layer 820 may comprise a softermaterial than the polymeric member 812. The relatively softer materiallayer 820 may provide for an amount of compliance or movement betweenthe components (e.g., electrical connections, solder joints, etc.) onthe electronic board 808 and the polymeric material 812. This may helpto limit or prevent loading the electronic components above a failurepoint when the electronic board 808 is subjected to a mechanical wave.In an embodiment, the material layer 820 may be disposed over at leastone solder joint.

In an embodiment, the sensing subassembly 800 comprising the shockprotection apparatus 802 may be used to protect an electronic componentfrom a mechanical wave. When a mechanical wave is incident upon and/ortravels through the housing 804 containing an electronic component suchas an electronic board 808 disposed in the cavity 806, a stiffeningmember 810 coupled to the electronic board 808 and a polymeric material812 disposed about the electronic board 808 may attenuate the mechanicalwave to limit the amplitude and/or frequencies impacting the electronicboard 808. The polymeric material 812 disposed on at least a portion ofthe electronic board 808 may provide a secondary load path and/orsupport for at least one solder joint on the electronic board 808. Themechanical wave may be attenuated in the axial and radial directionsalong the axis of the subassembly 802. The stiffening member 810 mayengage the electronic board 808 and one or more spring members 822, 824may be disposed on at least a portion of the electronic board 808. In anembodiment, a spring members 822, 824 may be coupled to the electronicboard 808 and the cavity 806. The spring members 822, 824 may supportone or more electronic components disposed on the electronic board 808and aid in protecting the electronic components from the mechanical waveincluding, for example, any resulting inertial loads on the electronicboard. In an embodiment, first spring member 822 may be disposed on atleast a first end of the electronic board 808 and a second spring member824 may be disposed on at least a second end of the electronic board 808to couple the tubular member 816 within the cavity 806. In anembodiment, the electronic board 808 may be utilized to carry out atleast one function after the sensing subassembly 800 experiences atleast one mechanical wave resulting from a perforating event.

In an embodiment, a sensing subassembly 900 may comprise a shockprotection apparatus used to protect a sensor 908 disposed within thesensing subassembly 900. As shown in FIGS. 10, 11, and 12, the sensingsubassembly 900 comprises a housing 904, a cavity 906 disposed withinthe housing 904, and at least one sensor 908 disposed within the cavity906. The shock protection apparatus 902 comprise at least one isolatingmember 910 disposed within the cavity 906 about at least a portion ofthe sensor 908. The at least one isolating member 910 is configured toattenuate at least a portion of the frequency components of a mechanicalwave above a threshold frequency (e.g., above a given frequency, above afrequency amplitude, etc.) and transmit at least a portion of frequencycomponents below the threshold to the at least one sensor 908. In anembodiment, the shock protection apparatus 902 may be configured tomaintain the functional integrity of the at least one sensor 908disposed within the cavity 906 while in close proximity to a perforatinggun during a perforating event.

In an embodiment, the cavity 906 may be disposed within the housing 904and configured so that the housing 904 surrounds the cavity 906. In thisembodiment, a sensor 908 disposed within the cavity 906 may not beexposed to the exterior of the housing 904 in any direction. In someembodiments, the cavity 906 may be disposed so that at least one side ofthe cavity 906 is exposed to the exterior of the cavity 906 and/or theinterior of the sensing subassembly 902 (e.g., the interior volume ofthe shock protection apparatus 900). This configuration may allow foreasier insertion of at least one sensor 908 such as an accelerometerinto the cavity 906.

At least one sensor 908 may disposed within the cavity 906 of thehousing 904 of the shock protection apparatus 500. In an embodiment, thesensor 908 may comprise an accelerometer. As disclosed in FIGS. 10 and11, three sensors 908 may be disposed within the cavity 906. In anembodiment, the sensors 908 may be mounted on a mounting member 912.Furthermore, as disclosed in FIGS. 10 and 11, three sensors 908 aremounted on a triaxial mounting member 912 so that each sensor 908 maysense a parameter in all three Cartesian directional coordinates. In anembodiment, the mounting member 912 may be a cube shape, a sphericalshape, or any shape that would function to mount at least one sensor908.

In an embodiment, the isolating member 910 may be disposed within thecavity 906 and configured to attenuate at least a portion of frequencycomponents of a mechanical wave above a threshold and transmit at leasta portion of frequency components below the threshold frequency to theat least one sensor 908. The isolation member 910 may engage at leastone portion of at least one side of the cavity 906, and the isolationmember 910 may encapsulate the at least one sensor 908 and/or a mountingmember 912. In an embodiment, the isolation member 910, may comprise apolymeric material configured to provide a spring function around the atleast one sensor. This feature may reduce deflection and/or damage tothe at least one sensor 908.

In an embodiment, the isolation member 910 may provide for sufficientcompliance to allow for effective isolation of the sensor from at leasta portion of the mechanical wave above a threshold frequency, which maycomprise a frequency content that may cause damage to the sensor 908. Inthis embodiment, the threshold frequency may be between about 10 kHz andabout 100 kHz, between about 20 kHz and about 50 kHz, or between about25 kHz and about 40 kHz. In an embodiment, the threshold frequency maybe about 30 kHz. The desired threshold frequency may be obtained in one,two, and/or three axes based at least in part on the modulus of theisolation member 910 and the geometry of the isolation member 910 (e.g.,thickness, depth, etc.) around the at least one sensor 908 and/or themounting member 912. The isolation member 910 may also providesufficient compliance to allow for effective isolation of a mountingmember 912. Since the isolation member 910 may attenuate frequenciesabove a threshold frequency and transmit frequency below a thresholdfrequency, an accelerometer, for example, may sense desired parametersbelow a threshold frequency while avoiding damage and interference fromfrequencies above a threshold frequency.

In an embodiment, the polymeric material may comprise a glass transitiontemperature above the expected operating conditions within the wellbore.This feature may allow for isolation performance at elevated workingtemperatures. For example, when the polymer exceeds the glasstransition, it may soften and attenuate frequencies lower than desired.Furthermore, a glass transition temperature above the expected operatingtemperature may prevent the isolation member from transitioning andflowing when the shock protection apparatus 900 is in place within thewarmer temperatures of the wellbore. In an embodiment, the glasstransition temperature may be above about 100 degrees Celsius, aboveabout 125 degrees Celsius, above about 150 degrees Celsius, above about175 degrees Celsius, or above about 200 degrees Celsius. In anembodiment, the glass transition temperature may be below about 300degrees Celsius.

A method of measuring a mechanical wave event in a wellbore comprisesdisposing a sensing subassembly 900 comprising shock protectionapparatus 902 into a wellbore. The shock protection apparatus 902 mayreceive at least one mechanical wave within the wellbore, which mayinclude a shock wave and/or a pressure disturbance. When the shockprotection apparatus 902 receives at least one mechanical wave, theshock protection apparatus 902 attenuates at least a portion offrequency components of at least one mechanical wave above a thresholdand transmits at least a portion of the frequency components below thethreshold to the sensor 908. The sensor 908 senses at least oneparameter associated with the mechanical wave and generates at least onesignal in response to sensing at least one parameter. The at least onesignal may then be stored in a non-transitory computer readable media914. The at least one mechanical wave may comprises a shock wavegenerated by at least one perforation gun disposed in a wellbore.

A method of absorbing mechanical waves using a shock protectionapparatus 902 comprises, in an embodiment, attenuating at least aportion of a mechanical wave and transmitting at least a portion of themechanical wave to the at least one sensor 908. The sensor 908 may senseat least one parameter of the mechanical wave transmitted through theisolation member 910. The isolation member 910 may encapsulate the atleast one sensor 908. The isolation member 910 may comprise a polymericmaterial configured to provide a spring function around the at least onesensor 908. Additionally, a mounting member 912 may be utilized to mountat least one sensor 908. In an embodiment, the isolation member 910 mayencapsulate the mounting member 912. Additionally, in an embodiment, theshock protection apparatus 900 and/or the isolation member 910 mayattenuate at least a portion of the mechanical wave above a thresholdfrequency and transmit at least a portion of the mechanical wave below athreshold frequency to the at least one sensor 908. In an embodiment,the shock protection apparatus 902 and/or the isolation member 910 mayattenuate mechanical wave frequencies at about 30 kHz or greater andtransmitting mechanical wave frequencies below about 30 kHz.

Having described the systems and methods, various embodiments mayinclude, but are not limited to:

In an embodiment, a sensing subassembly for use with a downhole toolcomprises a housing, a cavity disposed within the housing, at least oneelectronic component disposed within the cavity, and at least oneisolating member disposed within the cavity. The at least one isolatingmember is configured to attenuate at least a portion of frequencycomponents of a mechanical wave above a threshold and transmit at leasta portion of frequency components below the threshold to the at leastone electronic device. The sensing subassembly may also include amounting member configured for mounting the at least one electronicdevice. The mounting member may comprise a triaxial mount configured fororienting at least one electronic device in three axes. The at least oneisolating member may comprise a polymeric material configured to providea spring function around the at least one electronic device. Theisolation member may comprise a polymeric material configured to providea spring function around the mounting member. The threshold may be about30 kHz or greater. The at least one isolating member may be furtherconfigured to maintain the functional integrity of the at least oneelectronic device disposed within the cavity while in close proximity toa detonating perforating gun. The polymeric material may comprise aglass transition temperature above about 100 degrees Celsius. Thethreshold may be based on the modulus or thickness of the polymericmaterial around the at least one electronic device. The threshold may bebased on the modulus or thickness of the polymeric material around themounting member. The isolation member may engage at least a portion ofthe cavity wall. The cavity may extend into the housing.

In an embodiment, a method of measuring a shock event in a wellborecomprises receiving, by a sensing subassembly, at least one mechanicalwave within a wellbore, where the sensing subassembly comprises: acavity disposed within a housing, at least electronic component disposedwithin the cavity, and at least one isolating member disposed with theat least one electronic device within the cavity. The method alsocomprises attenuating at least a portion of frequency components of theat least one mechanical wave above a threshold frequency, transmittingat least a portion of the frequency components of the at least onemechanical wave below the threshold to the electronic device, sensing atleast one parameter associated with the at least one mechanical wave,generating, by the electronic component, at least one signal in responseto the sensing, and storing the at least one signal in a non-transitorycomputer readable media. The at least one mechanical wave may comprise adetonation wave generated by at least one perforating gun disposedwithin the wellbore.

In an embodiment, a method of absorbing a mechanical wave using a shockprotection apparatus comprises receiving a mechanical wave at a housing.The housing is disposed in a wellbore, and the housing contains at leastone cavity with at least one sensor disposed within the at least onecavity. The at least one sensor is coupled to the housing by anisolation member. The method also comprises attenuating at least aportion of the mechanical wave using the isolation member, transmittingat least a portion of the mechanical wave to the at least one sensorusing the isolation member, and sensing at least one parameter of themechanical wave transmitted to the at least one sensor. The method mayalso include encapsulating the at least one sensor with the isolationmember, and the isolation member may comprise a polymeric materialconfigured to provide a spring function around the at least one sensor.The method may also include mounting the at least one sensor on amounting member. The method may also include encapsulating the mountingmember with the isolation member, and the isolation member may comprisea polymeric material configured to provide a spring function around themounting member. Attenuating at least the portion of the mechanical wavemay comprise attenuating above a threshold frequency, and transmittingat least a portion of the mechanical wave may comprise transmittingbelow a threshold frequency to the at least one sensor. Attenuating atleast a portion of the mechanical wave may comprise attenuatingmechanical wave frequencies at about 30 kHz or greater, and transmittingmechanical wave frequencies may comprise transmitting mechanical wavefrequencies below about 30 kHz.

It is to be understood that the various embodiments described herein maybe utilized in various orientations, such as inclined, inverted,horizontal, vertical, etc., and in various configurations, withoutdeparting from the principles of the present disclosure. The embodimentsare described merely as examples of useful applications of theprinciples of the disclosure, which is not limited to any specificdetails of these embodiments.

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R_(l), and an upperlimit, R_(u), is disclosed, any number falling within the range isspecifically disclosed. In particular, the following numbers within therange are specifically disclosed: R=R_(l)+k*(R_(u)−R_(l)), wherein k isa variable ranging from 1 percent to 100 percent with a 1 percentincrement, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent,96 percent, 97 percent, 98 percent, 99 percent, or 100 percent.Moreover, any numerical range defined by two R numbers as defined in theabove is also specifically disclosed. Use of the term “optionally” withrespect to any element of a claim means that the element is required, oralternatively, the element is not required, both alternatives beingwithin the scope of the claim. Use of broader terms such as comprises,includes, and having should be understood to provide support fornarrower terms such as consisting of, consisting essentially of, andcomprised substantially of. Accordingly, the scope of protection is notlimited by the description set out above but is defined by the claimsthat follow, that scope including all equivalents of the subject matterof the claims. Each and every claim is incorporated as furtherdisclosure into the specification and the claims are embodiment(s) ofthe present invention.

What is claimed is:
 1. A sensing subassembly for use with a downholetool comprising: a housing; a cavity, wherein the cavity is disposedwithin the housing; at least one electronic component disposed withinthe cavity; and at least one isolating member disposed within thecavity, wherein the at least one isolating member is configured toattenuate at least a portion of frequency components of a mechanicalwave above a threshold and transmit at least a portion of frequencycomponents below the threshold to the at least one electronic device. 2.The sensing subassembly of claim 1, further comprising a mounting memberconfigured for mounting the at least one electronic device.
 3. Thesensing subassembly of claim 2, wherein the mounting member comprises atriaxial mount configured for orienting at least one electronic devicein three axes.
 4. The sensing subassembly of claim 1, wherein the atleast one isolating member comprises a polymeric material configured toprovide a spring function around the at least one electronic device. 5.The sensing subassembly of claim 2, wherein the isolation membercomprises a polymeric material configured to provide a spring functionaround the mounting member.
 6. The sensing subassembly of claim 1,wherein the threshold is about 30 kHz or greater.
 7. The sensingsubassembly of claim 1, wherein the at least one isolating member isfurther configured to maintain the functional integrity of the at leastone electronic device disposed within the cavity while in closeproximity to a detonating perforating gun.
 8. The sensing subassembly ofclaim 4, wherein the polymeric material comprises a glass transitiontemperature above about 100 degrees Celsius.
 9. The sensing subassemblyof claim 4, wherein the threshold is based on the modulus or thicknessof the polymeric material around the at least one electronic device. 10.The sensing subassembly of claim 5, wherein the threshold is based onthe modulus or thickness of the polymeric material around the mountingmember.
 11. The sensing subassembly of claim 1, wherein the isolationmember engages at least a portion of the cavity wall.
 12. The sensingsubassembly of claim 1, wherein the cavity extends into the housing. 13.A method of measuring a shock event in a wellbore comprising: receiving,by a sensing subassembly, at least one mechanical wave within awellbore, wherein the sensing subassembly comprises: a cavity disposedwithin a housing, at least electronic component disposed within thecavity, and at least one isolating member disposed with the at least oneelectronic device within the cavity; attenuating at least a portion offrequency components of the at least one mechanical wave above athreshold frequency; transmitting at least a portion of the frequencycomponents of the at least one mechanical wave below the threshold tothe electronic device; sensing at least one parameter associated withthe at least one mechanical wave; generating, by the electroniccomponent, at least one signal in response to the sensing; and storingthe at least one signal in a non-transitory computer readable media. 14.The method of claim 13, wherein the at least one mechanical wavecomprises a detonation wave generated by at least one perforating gundisposed within the wellbore.
 15. A method of absorbing a mechanicalwave using a shock protection apparatus comprising: receiving amechanical wave at a housing, wherein the housing is disposed in awellbore, wherein the housing contains at least one cavity with at leastone sensor disposed within the at least one cavity, wherein the at leastone sensor is coupled to the housing by an isolation member; attenuatingat least a portion of the mechanical wave using the isolation member;transmitting at least a portion of the mechanical wave to the at leastone sensor using the isolation member; and sensing at least oneparameter of the mechanical wave transmitted to the at least one sensor.16. The method of claim 15, further comprising encapsulating the atleast one sensor with the isolation member, wherein the isolation membercomprises a polymeric material configured to provide a spring functionaround the at least one sensor.
 17. The method of claim 15, furthercomprising mounting the at least one sensor on a mounting member. 18.The method of claim 17, further comprising encapsulating the mountingmember with the isolation member, wherein the isolation member comprisesa polymeric material configured to provide a spring function around themounting member.
 19. The method of claim 15, wherein attenuating atleast the portion of the mechanical wave comprises attenuating above athreshold frequency and wherein transmitting at least a portion of themechanical wave comprises transmitting below a threshold frequency tothe at least one sensor.
 20. The method of claim 19, wherein attenuatingat least a portion of the mechanical wave comprises attenuatingmechanical wave frequencies at about 30 kHz or greater and transmittingmechanical wave frequencies comprises transmitting mechanical wavefrequencies below about 30 kHz.